Merge remote-tracking branch 'upstream/master'

46 files changed, 2345 insertions, 1515 deletions

diff --git a/challenge-027/paulo-custodio/Makefile b/challenge-027/paulo-custodio/Makefile
new file mode 100644
index 0000000000..c3c762d746
--- /dev/null
+++ b/challenge-027/paulo-custodio/Makefile
@@ -0,0 +1,2 @@
+all:
+	perl ../../challenge-001/paulo-custodio/test.pl
diff --git a/challenge-027/paulo-custodio/README b/challenge-027/paulo-custodio/README
new file mode 100644
index 0000000000..87dc0b2fbd
--- /dev/null
+++ b/challenge-027/paulo-custodio/README
@@ -0,0 +1 @@
+Solution by Paulo Custodio
diff --git a/challenge-027/paulo-custodio/perl/ch-1.pl b/challenge-027/paulo-custodio/perl/ch-1.pl
new file mode 100644
index 0000000000..e4b4feca3e
--- /dev/null
+++ b/challenge-027/paulo-custodio/perl/ch-1.pl
@@ -0,0 +1,23 @@
+#!/usr/bin/perl
+
+# Challenge 027
+#
+# Task #1
+# Write a script to find the intersection of two straight lines. The
+# co-ordinates of the two lines should be provided as command line parameter.
+# For example:
+#
+# The two ends of Line 1 are represented as co-ordinates (a,b) and (c,d).
+#
+# The two ends of Line 2 are represented as co-ordinates (p,q) and (r,s).
+#
+# The script should print the co-ordinates of point of intersection of the
+# above two lines.
+
+use Modern::Perl;
+
+my($x1,$y1,$x2,$y2,$x3,$y3,$x4,$y4) = @ARGV;
+my $D = ($x1-$x2)*($y3-$y4)-($y1-$y2)*($x3-$x4);
+my $x = (($x1*$y2-$y1*$x2)*($x3-$x4)-($x1-$x2)*($x3*$y4-$y3*$x4))/$D;
+my $y = (($x1*$y2-$y1*$x2)*($y3-$y4)-($y1-$y2)*($x3*$y4-$y3*$x4))/$D;
+say sprintf("%.1f %.1f", $x, $y);
diff --git a/challenge-027/paulo-custodio/perl/ch-2.pl b/challenge-027/paulo-custodio/perl/ch-2.pl
new file mode 100644
index 0000000000..8091076b58
--- /dev/null
+++ b/challenge-027/paulo-custodio/perl/ch-2.pl
@@ -0,0 +1,38 @@
+#!/usr/bin/perl
+
+# Challenge 027
+#
+# Task #2
+# Write a script that allows you to capture/display historical data. It could
+# be an object or a scalar. For example
+#
+# my $x = 10; $x = 20; $x -= 5;
+#
+# After the above operations, it should list $x historical value in order.
+
+use Modern::Perl;
+
+{
+    package LoggingScalar;
+    sub TIESCALAR {
+        my($class, $value) = @_;
+        return bless [$value], $class;
+    }
+    sub FETCH {
+        my($self) = @_;
+        return $self->[-1];
+    }
+    sub STORE {
+        my($self, $value) = @_;
+        push @$self, $value;
+    }
+    sub show_hist {
+        my($self) = @_;
+        say join(" ", @$self);
+    }
+}
+
+tie my $x, 'LoggingScalar', 10;
+$x = 20;
+$x -= 5;
+tied($x)->show_hist();
diff --git a/challenge-027/paulo-custodio/python/ch-1.py b/challenge-027/paulo-custodio/python/ch-1.py
new file mode 100644
index 0000000000..8f3e6c9731
--- /dev/null
+++ b/challenge-027/paulo-custodio/python/ch-1.py
@@ -0,0 +1,23 @@
+#!/usr/bin/python3
+
+# Challenge 027
+#
+# Task #1
+# Write a script to find the intersection of two straight lines. The
+# co-ordinates of the two lines should be provided as command line parameter.
+# For example:
+#
+# The two ends of Line 1 are represented as co-ordinates (a,b) and (c,d).
+#
+# The two ends of Line 2 are represented as co-ordinates (p,q) and (r,s).
+#
+# The script should print the co-ordinates of point of intersection of the
+# above two lines.
+
+import sys
+
+x1,y1,x2,y2,x3,y3,x4,y4 = [int(x) for x in sys.argv[1:9]]
+D = (x1-x2)*(y3-y4)-(y1-y2)*(x3-x4)
+x = ((x1*y2-y1*x2)*(x3-x4)-(x1-x2)*(x3*y4-y3*x4))/D
+y = ((x1*y2-y1*x2)*(y3-y4)-(y1-y2)*(x3*y4-y3*x4))/D
+print("{:.1f} {:.1f}".format(x, y))
diff --git a/challenge-027/paulo-custodio/python/ch-2.py b/challenge-027/paulo-custodio/python/ch-2.py
new file mode 100644
index 0000000000..99fd57554b
--- /dev/null
+++ b/challenge-027/paulo-custodio/python/ch-2.py
@@ -0,0 +1,26 @@
+#!/usr/bin/python3
+
+# Challenge 027
+#
+# Task #2
+# Write a script that allows you to capture/display historical data. It could
+# be an object or a scalar. For example
+#
+# my $x = 10; $x = 20; $x -= 5;
+#
+# After the above operations, it should list $x historical value in order.
+
+class LoggingScalar:
+    def __init__(self, value):
+        self.values = [value]
+    def set(self, value):
+        self.values.append(value)
+    def get(self):
+        return self.values[-1]
+    def show_hist(self):
+        print(" ".join([str(x) for x in self.values]))
+
+x = LoggingScalar(10)
+x.set(20)
+x.set(x.get()-5)
+x.show_hist()
diff --git a/challenge-027/paulo-custodio/t/test-1.yaml b/challenge-027/paulo-custodio/t/test-1.yaml
new file mode 100644
index 0000000000..31ebb25d9b
--- /dev/null
+++ b/challenge-027/paulo-custodio/t/test-1.yaml
@@ -0,0 +1,5 @@
+- setup:
+  cleanup:
+  args:     15 10 49 25 29 5 32 32
+  input:
+  output:   30.3 16.8
diff --git a/challenge-027/paulo-custodio/t/test-2.yaml b/challenge-027/paulo-custodio/t/test-2.yaml
new file mode 100644
index 0000000000..78447f751a
--- /dev/null
+++ b/challenge-027/paulo-custodio/t/test-2.yaml
@@ -0,0 +1,5 @@
+- setup:
+  cleanup:
+  args:
+  input:
+  output:   10 20 15
diff --git a/challenge-143/alexander-pankoff/perl/ch-1.pl b/challenge-143/alexander-pankoff/perl/ch-1.pl
new file mode 100755
index 0000000000..fcb9c8edbc
--- /dev/null
+++ b/challenge-143/alexander-pankoff/perl/ch-1.pl
@@ -0,0 +1,7 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+my $expr = $ARGV[0];
+die "invalid expr\n" unless $expr && $expr =~ m/^[\s\d\.\+\-\*\(\)]*$/;
+print eval($expr) . "\n";
diff --git a/challenge-143/alexander-pankoff/perl/ch-2.pl b/challenge-143/alexander-pankoff/perl/ch-2.pl
new file mode 100755
index 0000000000..a952866cde
--- /dev/null
+++ b/challenge-143/alexander-pankoff/perl/ch-2.pl
@@ -0,0 +1,61 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+use feature qw'say signatures';
+no warnings qw'experimental::signatures';
+
+use List::Util qw'first';
+
+use constant DEBUG => $ENV{DEBUG} // 0;
+
+run() unless caller();
+
+sub run() {
+    my $stealthy = stealthy( $ARGV[0] );
+    say $stealthy ? 1 : 0;
+    explain($stealthy) if DEBUG;
+}
+
+sub stealthy($n) {
+    my @divisors = find_divisors_pairs($n);
+    my @pairs    = pairs(@divisors);
+
+    my $stealthy = first {
+        my ( $a, $b, $c, $d ) = flatten($_);
+        $a * $b == $c * $d && $a + $b == $c + $d + 1;
+    }
+    @pairs;
+
+    return $stealthy;
+}
+
+sub explain($stealthy) {
+    say "Not stealthy" && return if !$stealthy;
+    my ( $a, $b, $c, $d ) = flatten($stealthy);
+    say
+"Since $a (a) * $b (b) = $c (c) * $d (d) and $a (a) + $b (b) = $c (c) + $d (d) + 1";
+}
+
+sub pairs(@xs) {
+    my @out;
+    for my $i ( 0 .. $#xs - 1 ) {
+        push @out, map { [ $xs[$i], $xs[$_] ] } ( $i + 1 .. $#xs );
+    }
+    return @out;
+}
+
+sub flatten($xs) {
+    map { @$_ } @$xs;
+}
+
+sub find_divisors_pairs($x) {
+    my @out;
+    my $max = sqrt($x);
+    for my $i ( 1 .. $max ) {
+        if ( $x % $i == 0 ) {
+            push @out, [ $i, $x / $i ];
+        }
+    }
+
+    return @out;
+}
diff --git a/challenge-143/conor-hoekstra/apl/ch-1.apl b/challenge-143/conor-hoekstra/apl/ch-1.apl
new file mode 100644
index 0000000000..ec5e3506f0
--- /dev/null
+++ b/challenge-143/conor-hoekstra/apl/ch-1.apl
@@ -0,0 +1,5 @@
+solution ←  ⍎'×'@('*'∘=)
+
+⍝ Tests
+solution '10 + 20 - 5'       ⍝ 25
+solution '(10 + 20 - 5) * 2' ⍝ 50
diff --git a/challenge-143/conor-hoekstra/apl/ch-2.apl b/challenge-143/conor-hoekstra/apl/ch-2.apl
new file mode 100644
index 0000000000..2c5bcceda9
--- /dev/null
+++ b/challenge-143/conor-hoekstra/apl/ch-2.apl
@@ -0,0 +1,4 @@
+solution ← {1∊2-/(⍵∘÷+⊢)∪⍵∨⍳⌊⍵*.5}
+
+⍝ Tests
+solution ¨ 36 12 6 ⍝ 1 1 0
diff --git a/challenge-143/dave-jacoby/blog.txt b/challenge-143/dave-jacoby/blog.txt
new file mode 100644
index 0000000000..c3e15f2677
--- /dev/null
+++ b/challenge-143/dave-jacoby/blog.txt
@@ -0,0 +1 @@
+https://jacoby.github.io/2021/12/14/ninja-numbers-hiding-in-trees-the-weekly-challenge-143.html
diff --git a/challenge-143/dave-jacoby/perl/ch-1.pl b/challenge-143/dave-jacoby/perl/ch-1.pl
new file mode 100644
index 0000000000..0caded391c
--- /dev/null
+++ b/challenge-143/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,62 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say state postderef signatures };
+no warnings qw{ experimental };
+
+my @examples;
+push @examples, '( 5 * 10 )  - ( 12 * 3 )';
+push @examples, '10 + 20 - 5';
+push @examples, '(10 + 20 - 5) * 2';
+push @examples, '( ( 10 * 20 ) - 5) * 2';
+
+for my $i (@examples) {
+    my $o  = calculator($i);
+    my $o2 = bc($i);
+    say <<"END";
+    Input:  \$i = $i
+    Output: $o
+    BC:     $o2
+END
+}
+
+sub calculator( $s) {
+
+    # parens
+    while ( $s =~ /\([\s\d\+\-\*]+\)/mix ) {
+        $s =~ s/\(([\s\d\+\-\*]+\))/calculator( unbracket( $1 ))/e;
+    }
+
+    # multiplication
+
+    while ( $s =~ / \d+ \s* \* \s* \d+ /mx ) {
+        $s =~ s/( (\d+) \s* \* \s* (\d+) )/ $2 * $3 /emx;
+    }
+
+    # addition
+
+    while ( $s =~ / \d+ \s* \+ \s* \d+ /mx ) {
+        $s =~ s/( (\d+) \s* \+ \s* (\d+) )/ $2 + $3 /emx;
+    }
+
+    # subtraction
+    while ( $s =~ / \d+ \s* \- \s* \d+ /mx ) {
+        $s =~ s/( (\d+) \s* \- \s* (\d+) )/ $2 - $3 /emx;
+    }
+    return $s;
+}
+
+sub unbracket( $s ) {
+    $s =~ s/^\(//;
+    $s =~ s/\)$//;
+    return $s;
+}
+
+# This is the easy way, using pre-existing code
+sub bc( $s) {
+    my $cmd = qq{ echo '$s' | bc  };
+    my $x   = qx{$cmd};
+    chomp $x;
+    return $x;
+}
diff --git a/challenge-143/dave-jacoby/perl/ch-2.pl b/challenge-143/dave-jacoby/perl/ch-2.pl
new file mode 100644
index 0000000000..c712e2014b
--- /dev/null
+++ b/challenge-143/dave-jacoby/perl/ch-2.pl
@@ -0,0 +1,41 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say postderef signatures state };
+no warnings qw{ experimental };
+
+my @examples = qw( 6 12 24 36 );
+
+for my $i (@examples) {
+    my $o = stealthy_numbers($i);
+    say <<"END";
+    Input:  \$n = $i
+    Output: $o
+END
+}
+
+sub stealthy_numbers ( $n ) {
+    my @factors = get_factor_pairs($n);
+    for my $i ( 0 .. -1 + scalar @factors ) {
+        my ( $ix, $iy ) = $factors[$i]->@*;
+        for my $j ( $i + 1 .. -1 + scalar @factors ) {
+            my ( $jx, $jy ) = $factors[$j]->@*;
+            my $addi = $ix + $iy;
+            my $addj = $jx + $jy;
+            return 1 if abs( $addi - $addj ) == 1;
+        }
+    }
+    return 0;
+}
+
+sub get_factor_pairs( $n ) {
+    my %hash;
+    for my $x ( map { int $_ } 1 .. $n ) {
+        next unless $n % $x == 0;
+        my $y  = $n / $x;
+        my $xy = join ',', sort { $a <=> $b } $x, $y;
+        $hash{$xy} = 1;
+    }
+    return map { [ split /,/, $_ ] } sort keys %hash;
+}
diff --git a/challenge-143/e-choroba/perl/ch-1.pl b/challenge-143/e-choroba/perl/ch-1.pl
new file mode 100755
index 0000000000..b1e25bec50
--- /dev/null
+++ b/challenge-143/e-choroba/perl/ch-1.pl
@@ -0,0 +1,62 @@
+#!/usr/bin/perl
+use warnings;
+use strict;
+
+sub calculator {
+    my ($expression) = @_;
+    while ($expression =~ m{[ ()]}) {
+        $expression =~ s/(-?\d+) (\*) (-?\d+)/$1 * $3/e;
+        $expression =~ s/(-?\d+) ([-+]) (-?\d+)/"$1 $2 $3"/ee;
+        $expression =~ s/\((-?\d+)\)/$1/g;
+    }
+    return $expression
+}
+
+use Marpa::R2;
+my $dsl = << '__DSL__';
+
+    lexeme default = latm => 1
+    :default ::= action => ::first
+
+    Expression ::= Number
+                 | ('(') Expression (')')   assoc => group
+                || Expression (ws asterisk ws) Expression  action => multiply
+                || Expression (ws plus ws) Expression      action => add
+                 | Expression (ws minus ws) Expression     action => subtract
+    Number     ::= Negative | positive
+    Negative   ::= minus positive                          action => neg
+
+    ws       ~ [\s]+
+    asterisk ~ '*'
+    plus     ~ '+'
+    positive ~ [\d]+
+    minus    ~ '-'
+
+__DSL__
+
+sub add      { $_[1] + $_[2] }
+sub subtract { $_[1] - $_[2] }
+sub multiply { $_[1] * $_[2] }
+sub neg      { -$_[2] }
+sub second   { $_[2] }
+
+my $grammar = 'Marpa::R2::Scanless::G'->new({source => \$dsl});
+
+sub calculate {
+    my ($input) = @_;
+    return ${ $grammar->parse(\$input, 'main') }
+}
+
+use Test2::V0;
+plan 8;
+
+my %tests = (
+    'Example 1' => ['10 + 20 - 5', 25],
+    'Example 2' => ['(10 + 20 - 5) * 2', 50],
+    Negative    => ['(1 + 2) - (1 * 12)', -9],
+    Precedence  => ['((-1 - -2 - -3 * -4 + -5))', -16]);
+
+for my $t (sort keys %tests) {
+    is calculator($tests{$t}[0]), $tests{$t}[1], "regex $t";
+    is calculate($tests{$t}[0]), $tests{$t}[1], "marpa $t";
+}
diff --git a/challenge-143/e-choroba/perl/ch-2.pl b/challenge-143/e-choroba/perl/ch-2.pl
new file mode 100755
index 0000000000..3feae62c6a
--- /dev/null
+++ b/challenge-143/e-choroba/perl/ch-2.pl
@@ -0,0 +1,24 @@
+#!/usr/bin/perl
+use warnings;
+use strict;
+use feature qw{ say };
+
+sub stealthy_number {
+    my ($n) = @_;
+    my @divisors = (map $n / $_, grep 0 == $n % $_, 1 .. sqrt $n);
+    for my $A (@divisors) {
+        for my $C (@divisors) {
+            my $B = $n / $A;
+            my $D = $n / $C;
+            return 1 if $A + $B == $C + $D + 1;
+        }
+    }
+    return 0
+}
+
+use Test2::V0;
+plan 3;
+
+is stealthy_number(36), 1, 'Example 1';
+is stealthy_number(12), 1, 'Example 2';
+is stealthy_number(6), 0, 'Example 3';
diff --git a/challenge-143/luca-ferrari/blog-1.txt b/challenge-143/luca-ferrari/blog-1.txt
new file mode 100644
index 0000000000..fbfeba6f6c
--- /dev/null
+++ b/challenge-143/luca-ferrari/blog-1.txt
@@ -0,0 +1 @@
+https://fluca1978.github.io/2021/12/13/PerlWeeklyChallenge143.html#task1
diff --git a/challenge-143/luca-ferrari/blog-2.txt b/challenge-143/luca-ferrari/blog-2.txt
new file mode 100644
index 0000000000..d7ed898652
--- /dev/null
+++ b/challenge-143/luca-ferrari/blog-2.txt
@@ -0,0 +1 @@
+https://fluca1978.github.io/2021/12/13/PerlWeeklyChallenge143.html#task2
diff --git a/challenge-143/luca-ferrari/blog-3.txt b/challenge-143/luca-ferrari/blog-3.txt
new file mode 100644
index 0000000000..bd24cc0a68
--- /dev/null
+++ b/challenge-143/luca-ferrari/blog-3.txt
@@ -0,0 +1 @@
+https://fluca1978.github.io/2021/12/13/PerlWeeklyChallenge143.html#task2pg
diff --git a/challenge-143/luca-ferrari/postgresql/ch-2.sql b/challenge-143/luca-ferrari/postgresql/ch-2.sql
new file mode 100644
index 0000000000..4f67625b37
--- /dev/null
+++ b/challenge-143/luca-ferrari/postgresql/ch-2.sql
@@ -0,0 +1,32 @@
+CREATE OR REPLACE FUNCTION f_stealth( needle int )
+  RETURNS int
+AS $CODE$
+  WITH numbers AS ( SELECT generate_series( 2, needle ) as n )
+  , pairs AS ( 
+    SELECT needle as n
+           , n as divisor
+           , needle / n as divisor_2
+           , case needle % n
+             when 0 then n + needle / n
+             else null
+             end as summix
+      from numbers
+  )
+  , stealth as (
+    select *
+           , abs( summix - lag( summix, 1, summix )  over ( ORDER BY summix DESC ) ) as lag
+           , abs( summix - lead( summix, 1, summix )  over ( ORDER BY summix DESC ) ) as lead
+      FROM pairs
+     where summix is not null
+  )
+
+  SELECT CASE count(*)
+         WHEN 0 THEN 0
+         ELSE 1
+           END
+  FROM stealth
+  WHERE ( lag = 1 or lead = 1 );
+
+
+  $CODE$
+    LANGUAGE sql;
diff --git a/challenge-143/luca-ferrari/raku/ch-1.p6 b/challenge-143/luca-ferrari/raku/ch-1.p6
new file mode 100644
index 0000000000..3ffbf3107b
--- /dev/null
+++ b/challenge-143/luca-ferrari/raku/ch-1.p6
@@ -0,0 +1,124 @@
+#!raku
+
+
+my Str $OPERATOR_ADD      = '+';
+my Str $OPERATOR_MINUS    = '-';
+my Str $OPERATOR_MULTIPLY = '*';
+my Str $OPERATOR_DIVIDE   = '/';
+
+
+
+
+grammar Calculator {
+    rule TOP {
+        ^ <expression> $
+    }
+
+    rule expression {
+        | <operation>+ %% $<operator>=([$OPERATOR_ADD|$OPERATOR_MINUS])
+        | <parenthesized-expression>
+    }
+    rule operation {
+        <operand>+  %% $<operator>=([$OPERATOR_MULTIPLY|$OPERATOR_DIVIDE])
+    }
+
+    rule operand {
+        | <number>
+        | <parenthesized-expression>
+    }
+
+    rule parenthesized-expression {
+        '(' <expression> ')'
+    }
+
+    token number { \d+ }
+}
+
+
+class CalculatorActions {
+    method TOP($/) {
+        $/.make: $<expression>.made
+    }
+
+
+    method parenthesized-expression($/) {
+        $/.make: $<expression>.made
+    }
+
+    method number($/) {
+        $/.make: +$/
+    }
+
+
+    method operand($/) {
+        $/.make: $<number> ?? $<number>.Int !! $<parenthesized-expression>.made;
+    }
+
+
+    # Computes a single operation in the form
+    # a + b
+    method do-compute( $left-operand, $operator, $right-operand ) {
+        given $operator {
+            when $OPERATOR_ADD      { $left-operand + $right-operand }
+            when $OPERATOR_MINUS    { $left-operand - $right-operand }
+            when $OPERATOR_MULTIPLY { $left-operand * $right-operand }
+            when $OPERATOR_DIVIDE   { $left-operand / $right-operand }
+        }
+    }
+
+
+    # Computes all the operation given the first operand, the set of operators
+    # and the other operands.
+    # For example:
+    # 1 + 2 * 3
+    # becomes
+    # do-compute-all( 1, [+,*], [2,3])
+    method do-compute-all( $left-operand is rw, @operators, @operands ) {
+        while ( @operators.elems > 0 ) {
+            $left-operand = self.do-compute( $left-operand,
+                                             @operators.pop,
+                                             @operands.pop );
+        }
+    }
+
+    method operation($/) {
+        # left part
+        my $result = $<operand>[ 0 ].made;
+
+        # if there is a right part ...
+        if $<operator> {
+            my @operators = $<operator>.map( *.Str );
+            my @operands  = $<operand>[ 1..* ].map( *.made );
+
+            self.do-compute-all( $result, @operators, @operands );
+        }
+
+        $/.make: $result;
+    }
+
+
+
+    method expression($/) {
+        if $<parenthesized-expression> {
+            $/.make: $<parenthesized-expression>.made
+        }
+        else {
+            my $result = $<operation>[ 0 ].made;     
+
+            if $<operator> {
+                my @operators = $<operator>.map( *.Str );
+                my @operands  = $<operation>[ 1..* ].map( *.made );
+
+                self.do-compute-all( $result, @operators, @operands );
+
+            }
+
+            $/.make: $result;
+        }
+    }
+}
+
+sub MAIN( Str $expr ) {
+    my $calculator = Calculator.parse( $expr, :actions( CalculatorActions ) );
+    "{ $expr } = { $calculator.made }".say;
+}
diff --git a/challenge-143/luca-ferrari/raku/ch-2.p6 b/challenge-143/luca-ferrari/raku/ch-2.p6
new file mode 100644
index 0000000000..b0be43e59c
--- /dev/null
+++ b/challenge-143/luca-ferrari/raku/ch-2.p6
@@ -0,0 +1,23 @@
+#!raku
+
+sub MAIN( Int $n where { $n > 0 }, Bool :$verbose = False  ) {
+    my @numbers = 1 ^..^ $n;
+
+    # extract all the pairs to get the $n by multiplication
+    my @pairs = @numbers.grep( $n %% * ).map( { $_, $n / $_, $_ + $n / $_ } );
+
+    # now extract all the pairs couples that have a difference of one
+    my $found = False;
+    for 0 ..^ @pairs.elems -> $left {
+        for $left ^..^ @pairs.elems -> $right {
+            if @pairs[ $left ][ 2 ] - @pairs[ $right ][ 2 ] == any( 1, -1 ) {
+                $found = True;
+                "$n is stealth by { @pairs[ $left ][ 0..1 ].join( ',' ) } and { @pairs[ $right ][ 0..1 ].join( ',' ) }".say  if $verbose;
+            }
+        }
+    }
+
+    "1".say and exit if $found;
+    "0".say;
+
+}
diff --git a/challenge-143/paulo-custodio/perl/ch-1.pl b/challenge-143/paulo-custodio/perl/ch-1.pl
index 90b6fe6506..73a806191b 100644
--- a/challenge-143/paulo-custodio/perl/ch-1.pl
+++ b/challenge-143/paulo-custodio/perl/ch-1.pl
@@ -3,10 +3,10 @@