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

my $csv = 'value1,value2,value3';
my $value = 'value1';

if ($csv =~ /(?:^|,)$value(?:,|$)/) {
    print "Yes\n";
} else {
    print "No\n";
}
if ($csv =~ /[,]$value[,]/) {
    print "Yes\n";
} else {
    print "No\n";
}