de2425 has asked for the wisdom of the Perl Monks concerning the following question:

Hi monks!

I was wondering if anyone could give me some quick help with a split problem I'm having. I actually don't even know if what I'm wanting to do will work but I hope someone can help.

What I'm wanting to do is to split by a variable that is a string that changes with each new read through of a file. I've tried:

@line=split(/$variable/,$_);

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but this doesn't seem to be giving me what I'm needing. Is there another way to specify a split based on a variable that is not constant?

Replies are listed 'Best First'.
Re: Split Help
by ikegami (Patriarch) on Mar 16, 2009 at 20:47 UTC
    Could it be that $variable contains text and not a regexp pattern? Fix: 
    my $sep_re = quotemeta($sep);

my @fields = split(/$sep_re/, $_);

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    or 
    my @fields = split(/\Q$sep/, $_);

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    For example, 

    $\ = "\n";
$, = ";";
for my $sep (",", "\t", "|") {
   my $line = join($sep, qw( a b c ));
   print $line;
   my @fields = split(/\Q$sep/, $line);
   print @fields;
   print '';
}

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    a,b,c
a;b;c

a       b       c
a;b;c

a|b|c
a;b;c

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    Or maybe you are trying to split on the two characters "\" and "t" instead of an actual tab character? 

    $\ = "\n";
$, = ";";
for my $sep ('\t', "\t") {
   print split(/\Q$sep/, "foo\tbar\\tbaz");
}

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    foo     bar;baz
foo;bar\tbaz

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Re: Split Help
by Sandy (Curate) on Mar 16, 2009 at 20:32 UTC
    Hi

    works for me. 

    [sandy]perl -e '$x="hello"; $y="thishelloyouhellotoday"; @a=split /$x/
+,$y; print "@a\n";'
this you today
[sandy]

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    could you give us an example of what doesn't work?

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[d/l]

      Thanks for the super quick response! What I'm trying to do is to use the split to count the occurrences of the filename with the file. I just checked with a print statement and I am getting a split but for some reason, I cannot get the correct number of splits. I can visually count them but I can't seem to get any goot results from something like:

      print "$#lines\n";

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[d/l]

        Hmm.. here you are saying 

        print "$#lines\n";

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        but in the OP 

        @line=split(/$variable/,$_);

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        Maybe you mean @lines? or perhaps $#line?

        If you include

        use warnings;

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        at the top of your program, perl helps you emitting a warning if, by typo, you are using a variable only once.

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        $#lines contains the last index of the array @lines which may or may not be one less than the actual number of elements in the array @lines.   To get the actual number of elements of an array you must use the array in scalar context: 

        print scalar @lines, "\n";

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Re: Split Help
by bellaire (Hermit) on Mar 16, 2009 at 20:33 UTC
    That should work just fine. We're going to need more context to judge what's wrong. For example, this code works perfectly: 
    my $variable = "x";
my @line = split(/$variable/,"aaaxbbbxccc");
print @line;

$variable = "y";
@line = split(/$variable/,"aaaybbbyccc");
print @line;

$variable = "z";
@line = split(/$variable/,"aaazbbbzccc");
print @line;

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    It prints aaabbbccc each time.
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Re: Split Help
by Marshall (Canon) on Mar 17, 2009 at 01:03 UTC
    There is some tricky stuff with split. 
    #!/usr/bin/perl -w
use strict;

my $a = "124 abc78980 abc 9872345987abcbca4321";
my $variable = "abc";
my @line=split(/$variable/,$a);
print join("\n",@line),"\n";
__END__
prints:
124 
78980 
 9872345987  #interesting
bca4321      #also interesting

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    It would be helpful if you could provide an input string and what you expect the output to be.
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