Assertions: Difference between revisions
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=={{header|Perl}}==
While not exactly an assertion, a common Perl idiom is to use <code>
<lang perl>open my $fh, '<', 'file' or die "Cannot open file: $!\n"; # $! contains the error message from the last error</lang>▼
Note: the above "or die" idiom is not needed when the "autodie" pragma is in use:▼
chomp(my $a = <>);
<lang perl>use autodie;▼
open my $fh, '<', 'file'; # automatically throws an exception on failure</lang>▼
▲<lang perl>my $a = 5;
$a == 42 or die "Error message\n";
# Alternatives
die "Error message\n" unless $a == 42;
die "Error message\n" if not $a == 42;
die "Error message\n" if $a != 42;</lang>
This idiom is typically used during file operations:
<lang perl>open my $fh, '<', 'file'
▲
▲<lang perl>use autodie;
▲open my $fh, '<', 'file'; # automatically throws an exception on failure</lang>
Some third-party modules provide other ways of using assertions in Perl:
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