I'll be damned. This reminds me of a story.

In about 2002 when I'd been hacking Perl quite a bit for 3 years I started to feel like I wanted to know how far I'd come. I was self-taught and pretty uneasy about my skills even though I'd accomplished some large projects, even an international one, at a large company. I looked around online till I found some Perl self-tests. There were three tests: beginner, moderate, expert. Feeling sheepish, I thought I'd better do the beginner first to get a good score and then move on. I expected to ace it.

I got like a 55% or something. I was so mad I blazed through the expert exam. Got 100% to my amazement. Being self-taught on real projects I knew references and objects and that sort of jazz pretty well, but I couldn't even answer some of the basics because they'd never come up.

In 9 years of Perl hacking, I did not know till now that there was a readline function in Perl or that there was anything else underlying the diamond operator.

readline are <> are two names for the same op (readline).

>perl -MO=Concise -e"<FH>"
5  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -e:1) v ->3
4     <1> readline[t2] vK/1 ->5
3        <#> gv[*FH] s ->4
-e syntax OK

>perl -MO=Concise -e"readline(*FH)"
6  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -e:1) v ->3
5     <1> readline[t2] vK/1 ->6
4        <1> rv2gv sKR/1 ->5
3           <#> gv[*FH] s ->4
-e syntax OK
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Similarly, ``, qx`` and readpipe are three names for the same op (backtick).

and and && are the same op, and or and || are the same op.

Finally, if and unless are implemented using the and and or ops respectively.

"and and && are the same op, and or and || are the same op."

I think there is a difference (precedence) between these ops...