When to use "or" and when to use || (double pipe) in Perl

Use || for assigning to a variable:

$a = $b || $c

Use "or" to control program flow:

$a = $b or die 'error: $b is unexpectedly false'

Mnemonic: || is a symbol like variables and numbers are, while "or" and "die" are both english words.

(source, source)

Perl: Disable control-C and control-Z

$SIG{'INT'} = 'IGNORE'; # Ctrl-C
$SIG{'TSTP'} = 'IGNORE'; # Ctrl-Z