http://www.perlmonks.org?node_id=229044

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

I often use =~ to see if a string contains a value such as $string=~"hello" but how do I see if a string does not contain a value? For example say if a string does not contain "hello" do this?

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Re: string does not contain
by pfaut (Priest) on Jan 22, 2003 at 15:34 UTC

    You can use !~ instead of =~. So, $string !~ "hello" would return true if the string doesn't contain "hello". See perlop (perldoc perlop) for more information on operators. 

    ---
print map { my ($m)=1<<hex($_)&11?' ':'';
$m.=substr('AHJPacehklnorstu',hex($_),1) }
split //,'2fde0abe76c36c914586c';

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Re: string does not contain
by broquaint (Abbot) on Jan 22, 2003 at 15:37 UTC
    Just use the negated version of the regex match operator !~ e.g 
    my $string = "foo bar baz";
print "no hello" if $string !~ /hello/;

__output__

no hello

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    See. perlop for more info.
    HTH

    _________
    broquaint

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Re: string does not contain
by aging acolyte (Pilgrim) on Jan 22, 2003 at 15:41 UTC
    TMTOWTDI

    negate the if to an unless: 

    
my $string = "foo bar baz";
print "no hello" unless $string =~ /hello/;

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    A.A.
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Re: string does not contain
by fredopalus (Friar) on Jan 22, 2003 at 15:46 UTC
    You may also want to look at perldoc perlretut. It explains the two operators (=~ and !~) right in the beginning.
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Re: string does not contain
by Hofmator (Curate) on Jan 23, 2003 at 13:07 UTC
    ... and as nobody mentioned it so far, if you just match against a literal string like 'hello', then you could also use the index function: 
    # if 'hello' not contained in $string
if ( index($string, 'hello' ) == -1) { 
  # do something
}

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    -- Hofmator

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Re: string does not contain
by OM_Zen (Scribe) on Jan 22, 2003 at 17:29 UTC
    Hi , 

    



     $string !=~ /hello/ 

     or

     unless($string =~ /hello/)

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    or that implies if not or a negate logic shall work for the not parsing a string value
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      Close.   Actually, $string !~ /hello/   or ! ( $string =~ /hello/ )
        p
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