I'm sure some of these have formal names and I'm just not aware of them.

• If you have a while loop (or a for loop you can make into a while loop) you can define the "while" after the command: print $n++ while ($n < 10)
• If you need to read everything from STDIN into a string: $var = join('',<>)
• As CeilingSpy pointed out, using $/ instead of \n is faster in some situations: print ('X'*10) . "\n"; is longer than print ('X'*10) . $/;
• Perl's say function is shorter than print, but you'll have to run the code with -M5.10.0
• Use ranges like a..z or even aa..zz. If needed as a string, use join.
• Incrementing strings: $z = 'z'; print ++$z; will display aa

That's all I can think of right now. I may add some more later.

I'm sure some of these have formal names and I'm just not aware of them.

• If you have a while loop (or a for loop you can make into a while loop) you can define the "while" after the command: print $n++ while ($n < 10)
• If you need to read everything from STDIN into a string: $var = join('',<>)
• As CeilingSpy pointed out, using $/ instead of \n is faster in some situations: print ('X'*10) . "\n"; is longer than print ('X'*10) . $/;
• Perl's say function is shorter than print, but you'll have to run the code with -E instead of -e
• Use ranges like a..z or even aa..zz. If needed as a string, use join.
• Incrementing strings: $z = 'z'; print ++$z; will display aa

That's all I can think of right now. I may add some more later.