or even with a match:

#!/usr/bin/perl
use strict;
use warnings;

my %factories = ( 'farms' => 'horses');
my $tmpf = 'farms';
my $match = "horses on the farm!";

print "$tmpf\n";   # prints 'farms'
print keys( %factories), "\n";   # 'farms' is one of them.
if ( defined $factories{$tmpf} ) {
    print "yay!\n" if $match =~ m/$factories{$tmpf}/;
}
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prints:

farms
farms
yay!
[download]