use strict;
my $str = '[cid:B54FD59F-8DE7-4ED1-A0C7-19E52F83A8D7]
[cid:
B54FD59F-8DE7-4ED1-A0C7-19E52F83A8D7]
[pid:B54FD59F-8DE7-4ED1-A0C7-19E52F83A8D7]
[cid:B54FD59F-8DE7-4ED1-A0C7-19E52F83A8D7]
[cid:B54FD]
[cid:B54FD59F-8DE7-4ED1-A0CU]-[3A8D7]-[19E52F83A8D7]
// lowercase won\'t match unless you include /i
[cid:2992S39a-1111-EEEE-9999-1239992EEIUE]';
my $regex = qr/(\[cid:(?:[0-9A-Z-]{7,8}){5}\])/p;
my $subst = '';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html