Your in looks like it might have a for loop inside it. Here's one way to write that up.

sub in {
  my ($coderef)= shift(@_);
  my ($match)= shift(@_);
  my (@vals)= @_;

  for ( @vals ) { $coderef->($match) if /$match/ }
}
[download]

Notice I had to toss in an extra parameter- a reference to a subroutine.

Another way to write this up is

sub in {
  my ($coderef)= shift(@_);
  my ($match)= shift(@_);
  my %dispatch = map { $_ => $coderef } @_;

  if ( exists $dispatch{$match} ) {
    $dispatch->($match);
  }
}
[download]

Shrug, it's another way, I guess.

What do you think?
I think that I can't look at your sub 'in' without either thinking, "Hey, this has a for loop inside it", or "Hey, this probably uses a dispatch table." :)

#!/usr/bin/perl

use strict;
use warnings;

sub in_dispatch {
  my ($coderef)= shift(@_);
  my ($match)= shift(@_);
  my %dispatch = map { $_ => $coderef } @_;

  if ( exists $dispatch{$match} ) {
    $dispatch{$match}->($match);
  }
}

sub in_array {
  my ($coderef)= shift(@_);
  my ($match)= shift(@_);
  my (@vals)= @_;

  for ( @vals ) { $coderef->($match) if /$match/ }
}

my $code = sub { my ($pal)= shift(@_);
                 print "Hello $pal!\n" ;
               };

my @pals = qw(Dick Jane Spot Samuel);
in_dispatch($code, 'George', @pals);  # no output
in_dispatch($code, 'Jane', @pals);    # Hello Jane!

in_list($code, 'Dick', @pals);      # Hello Dick!
in_list($code, 'Rover', @pals);     # no output
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But before you go using this for any life support systems, make sure you don't mind how both subs handle 'Sam' as the item to test ;)

Update Added #! line

blyman
setenv EXINIT 'set noai ts=2'