Using a Regexp to match a string exactly

brainbuz has asked for the wisdom of the Perl Monks concerning the following question:

I want to match a string exactly, consider:

my $C = shift ; my @others = grep ( !/$C/, @_ );

Now consider

$passtoC = 'Vanilla';
my @list = qw / Vanilla Vanilla_Orange_Sherbert Vanilla_Fudge_Swirl / ;

All items match vanilla and nothing is put into others.

My solution is:

my @others = grep ( !/^$C$/, @_ );

Which produces the desired result. I'm just wondering if there is a more direct way, or if there is any possible weirdness that might result from specifying both ^ and $ in the same regexp.

Comment on Using a Regexp to match a string exactly

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Re: Using a Regexp to match a string exactly by Ratazong (Monsignor) on Jan 27, 2010 at 07:46 UTC
Hi! There is no weirdness in using ^and $ in the same regex. However in your case, a simple compare (using `eq`) would also work. With the side-effect of making your code better readable and possibly faster. HTH, Rata	[reply] [d/l]
Re: Using a Regexp to match a string exactly by bart (Canon) on Jan 27, 2010 at 10:13 UTC
In Perl, there's no restriction for use of grep to just regexes! So: just use eq (or its inverse: ne) already. `my $C = shift ; my @others = grep $_ ne $C, @_;` [download] p.s. Unless there are more parameters following the grep call not intended for (this) grep, you may just as well drop the parens.	[reply] [d/l]
Re^2: Using a Regexp to match a string exactly by brainbuz (Novice) on Jan 28, 2010 at 03:17 UTC
Thanks, I was unaware that grep supported eq/ne!	[reply]
Re^3: Using a Regexp to match a string exactly by bart (Canon) on Jan 28, 2010 at 06:23 UTC
Not just `eq`/`ne`... but any expression that returns a true or false value — which implies: any expression in scalar context. (`undef`, `""` and 0 are false, anything else is true.) The generic variable `$_` holds the value of the current item from the list. Actually, it's even stronger than that: `$_` is an alias to the current item, which means: same value (by reference; you could say: same variable); different name. If you modify `$_` in that expression, the original value will have changed. Example: `@original= (0 .. 5); @true = grep $_*=2, @original; local $" = ", "; # for nicely formatted output print "original: @original\n"; print "output: @true\n";` [download] Result: `original: 0, 2, 4, 6, 8, 10 output: 2, 4, 6, 8, 10` [download] Each item in the original array has been doubled. Of those, only the nonzero (true) values have been come through the `grep` filter.	[reply] [d/l] [select]
Re: Using a Regexp to match a string exactly by Anonymous Monk on Jan 27, 2010 at 07:39 UTC
`if( "one" eq "two" ){ print "uh oh\n"; } else { print "perldoc perlop\n"; } __END__` [download] perldoc perlop	[reply] [d/l]