You've got the regex backwards - the text should be on the left and the pattern ('Plumbing') should be on the right: $str[1] =~ /$hash{$sic}{BUS}/;

index may be a faster alternative if you're looking for simple strings. See the examples below.

use strict;
use warnings;

my $substr = 'Plumbing';
my $string = 'ABC Plumbing';

my $pos = index( $string, $substr );

if( $pos )
{
    print "Found [$substr] in [$string] at $pos\n";
}
else
{
    print "[$substr] was not found in [$string]\n";
}

if( $string =~ m/$substr/ )
{
    print "Matched [$substr] in [$string]\n";
}
else
{
    print "[$substr] was not found in [$string]\n";
}
[download]

Output:

Found [Plumbing] in [ABC Plumbing] at 4
Matched [Plumbing] in [ABC Plumbing]
[download]