One problem is you are performing the second and third regexps on the default variable '$_'. I.e. what your code is actually doing is this: 
if ($MType =~ /-[45][15j]/ig  || 
    $_     =~ /[123][a46]u/ig ||
    $_     =~ /7[9l][hb]/ig   ) {
      print "\"red\"";
} else {    
      print "\"#CCFFCC\"";
}

[download]
I would also offer '$MType =~ /^(-(41|55|jj)|(1a|24|36)u)$/' as a regexp that would match all the cases you list (and no others).
However, if they are the only cases you want to match, creating a hash and checking for the existence of keys would be more efficient: 
my %matches;
foreach (qw( -41 -55 -jj 1au 24u 36u)) {
    $matches{$_} = '';
}

if (exists $matches{$MType}) {
    print "\"red\"";
} else {
    print "\"#CCFFCC\"";
}

[download]

In reply to Re: Regexp experts, come to rescue! by kilinrax
in thread Regexp experts, come to rescue! by bman

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