Conditionals

To do comparisons on different values, perl provides two sets of conditionals - one for numbers and one for strings.

Comparison	Strings	Numbers
Equality	eq	==
Inequality	ne	!=
Greater than	gt	>
Greater than or equal to	ge	>=
Less than	lt	<
Less than or equal to	le	<=
Comparison returns -1,0,1	cmp	<=>

It's important to use the right conditional - there are no "syntax" errors, so if you use a variable in the wrong context, there could be unexpected results.

You can build up conditionals using && (AND) and || (OR) operations.

Truth is a very flexible value in perl:

 
  ####  Some examples of truth: 
	1;		# traditionally 
	("a","b");	# the list has elements 
	" ";		# whitespace is true 
	"hello";	# strings are true 
	"00"		# a string 
  ####  Expressions that evaluate to false 
	0;		# traditionally 
	();		# the empty list 
	"";		# the null string 
	"0";		# The one string of non-zero length that is false.

The National Center for Supercomputing Applications
University of Illinois at Urbana-Champaign

[email protected]

Conditionals

Last modified: June 19, 1997