Substituting white spaces with a tab changes my string into numeric value

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

hi, I try to replace white spaces with tabs, but my string gets changed into a numeric value after that. I wrote the basic step as a new program to show what happens

#!/usr/bin/perl -w
use strict;

$_ = "CC1G_00040T0    NODE_4204_length_20667_cov_33.873905_4    3e-46"
+;

my $line = $_;
print "$line\n";
$line = s/\s+/\t/g;
print "$line\n";
[download]

when I run this, it gives the following:

CC1G_00040T0 NODE_4204_length_20667_cov_33.873905_4 3e-46

How can I prevent my string from becoming a numeric value?

Comment on Substituting white spaces with a tab changes my string into numeric value Download Code

Replies are listed 'Best First'.
Re: Substituting white spaces with a tab changes my string into numeric value by remiah (Hermit) on Sep 20, 2012 at 02:30 UTC
change $line = s/\s+/\t/g; to $line =~ s/\s+/\t/g;	[reply]
Re^2: Substituting white spaces with a tab changes my string into numeric value by PerlPeer (Novice) on Sep 20, 2012 at 02:33 UTC
Thanks!	[reply]
Re: Substituting white spaces with a tab changes my string into numeric value by dsheroh (Monsignor) on Sep 20, 2012 at 08:17 UTC
To explain what was going on here: `s/\s+/\t/g;` is equivalent to `$_ =~ s/\s+/\t/g;`, so `$line =~ s/\s+/\t/g;` actually means `$line = ($_ =~ s/\s+/\t/g);` (The parentheses aren't actually necessary, but I wanted to make the precedence completely clear.) In scalar context, a regex match or substitution (`=~`) returns the number of matches found/substitutions performed, so, to finally get to where that 2 comes from, `$line =~ s/\s+/\t/g;` changes all the groups of whitespace in `$_` into tabs and sets `$line` to the number of substitutions which were performed. If you look at `$_`, you will find that it holds the value you wanted, since `$line` and `$_` held the same value before the substitution was performed.	[reply] [d/l] [select]
Re^2: Substituting white spaces with a tab changes my string into numeric value by PerlPeer (Novice) on Sep 20, 2012 at 09:22 UTC
Thank you too. I figured that somehow I got a numerical value of the number of tabs, since when I used: `s/\s+/\t/` (thus without the "g") the number that was returned was 1 (instead of 2). I had no idea however, how this was caused. I frequently fail to recognize this kind of "equivalents". I hope this is just being new to perl.......	[reply] [d/l]