The question mark after a quantifier turns off greeding matching. In your regex it doesn't make much sense though. You're trying to match exactly 5 times, so greedy and non-greedy are the same thing.

/a{1,5}/;  # match 1-5 'a's prefer the longest.
/a{1,5}?/; # match 1-5 'a's prefer the shortest.
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Here is an example:

#!/usr/bin/perl -wT
use strict;

$_ = 'aaaab';

# greedily match upto 5 'a's followed by a word char 
print "Greedy:    ";
print /(a{1,5})\w/, "\n";

# non-greedily match upto 5 'a's followed by a word char
print "NonGreedy: ";
print /(a{1,5}?)\w/, "\n";

__END__
Greedy:    aaaa
NonGreedy: a
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-Blake