The following is untested. I'll describe what it's doing.

@parsed receives the captured matches. The captured matches will be the sub portion, followed by either the comment or nothing (using alternation, grouped by non-matching parens).

my @parsed;
if ( @parsed = $content =~
    /^\s*(sub\s+\w+).+?(?:(#.+)|())$/ )
        {
            local $, = "\n";
            print @parsed;
        }
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Dave

"If I had my life to do over again, I'd be a plumber." -- Albert Einstein