Perl 4 Package Separator
Instead of
utf8::decode $foo
Use
utf8'decode $foo
Chained comparison evaluation
In Perl v5.32+, comparisons chain such that something like $a < $b < $c evaluates as $a < $b && $b < $c. This means you can often shorten a conditional call to say:
$_>1&&say
$_>1>say
Variable reset
Several variables can be reset via various means:
$.=5;<>;say$. # 0 if there is nothing on STDIN
$@=5;eval;say$@ # ''
$!=5;-A;say 0+$! # 2
Glob assignment
In modern Perls you can't assign to a numeric variable greater than 0:
${0}=1;say$0 # OK
${1}=1;say$1 # Not OK (Modification of a read-only value)
But you can use a glob to bypass this:
*{1}=\1;say$1 # OK
Thelen's device
\ forces autovivication:
$a{5}++;say 0+%a # 1
\$b{5};say 0+%b # 1
You can use this, for example, to count unique values in a set:
\%a{1,1,2,4,2,4,4,2};say 0+%a # 3
Using $0
Sometimes $0 can be used as a useful store for when some condition is true or false.
Consider this solution to Sum of Divisors for OCaml Golf Competition:
#!perl -p
$'%$_ or$s+=$_ for//..($s=$_)/2;s/$/: $s/
This can be golfed a byte by storing the sum in $0:
#!perl -p
map${$'%-$_}+=$_,//..($0=$_)/2;s/$/: $0/