I'm a little confused by your spec - in cases like this, inclusion of a bit more of your input and output (preferably wrapped in <code> tags, Markup in the Monastery) might make things more obvious.

If you want to collect a series of regular expressions to test each line against, I would suggest using an array of regex references - see Regexp Quote Like Operators in perlop. That way each test is independent. I like to use the special variable $" to join the resulting regular expressions with alternators, though you could use grep to test each individually. Perhaps something like:

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

my @ignore_list = (
    qr/^\Qwords\:\:moreWords_\E\d+/i,
    qr/^[^:]+$/
);

local $" = '|';
while (<DATA>) {
    print unless /@ignore_list/;
}

__DATA__
words\:\:moreWords_68
words\:\:moreWords_92
words\:\:fewerWords_92
words\:\:moreWords_a7
birds\:\:moreWords_68
item
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