Instead of separating the lines of the poem (and the author) by colons, separate them with \n\t.

This way, you can replace

my ($line1, $line2, $line3, $author) = split ":", $poems{$number};
print "  $line1\n$line2\n   $line3\n\t$author\n";
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with

print "   ",$poems{$number},"\n";
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