Another guess at an answer to the rather vague original question: Statement Modifiers (see perlsyn).

>perl -wMstrict -le
"my $this_is_true = rand > 0.5;
 do_this_function() if $this_is_true;
 print q{i'm doing that!} while rand > 0.5;
 sub do_this_function { print q{i'm doing this!} }
"
i'm doing this!
i'm doing that!
i'm doing that!
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Update: New, improved example! Now with more modifiers!