CODEWITHSUNDEEP
regexperl
helloworld1234
helloworld1234

Reputation: 337

Perl: Regex - Unrecognized escape \s passed through

I have the following code:

use strict;
use warnings;

my $find = "(.*\s+)(subject:)(.*)(_1)(\s+.*)";
my $replace = '"\nsubject: \t\t$3_2"';

my $var_1 = "Time: 1000-1200    subject:    Physic_1    Class: Room A";
my $var_2 = "Time: 1000-1200    subject:    Math_1  Class: Room A";
$var_1 =~ s/$find/$replace/ee;
$var_2 =~ s/$find/$replace/ee;
print $var_1."\n";
print $var_2."\n";

I expect the output only extract the subject and change _1 to _2 like:

Output:
subject:      Physic_2
subject:      Math_2

However, what I get is:

Output:
Unrecognized escape \s passed through at test.pl line 20.
Unrecognized escape \s passed through at test.pl line 20.
Time: 1000-1200 subject:        Physic_1        Class: Room A
Time: 1000-1200 subject:        Math_1  Class: Room A

How can I escape those \t, \s+, \n as on string variable as perl regex pattern?

UPDATE: If I do something like this:

my $pattern = 's/(.*\s+)(subject:)(.*)(_1)(\s+.*)/\nsubject: \t\t$3_2/g';
my $var = "Time: 1000-1200   subject:    Physic_1    Class: Room A";
$var =~ $pattern;
print $var."\n";

It give the output, seem like nothing change:

Time: 1000-1200   subject:    Physic_1    Class: Room A

Upvotes: 0

Views: 5614

Answers (2)

choroba
choroba

Reputation: 242383

Double quotes interpolate backslashed characters. \s has a special meaning in a regex, but not in doublequotes - hence the warning. Use single quotes instead.

my $find = '(.*\s+)(subject:)(.*)(_1)(\s+.*)';

or, if you need double quotes for some other reasons, double the backslashes that should survive in the regex:

my $find = "(.*\\s+)(subject:)(.*)(_1)(\\s+.*)";

Upvotes: 4

Yunnosch
Yunnosch

Reputation: 26763

You can do that in the first line exactly as you did it in the second line: 

my $find = '(.*\s+)(subject:)(.*)(_1)(\s+.*)';

Output:

subject:                    Physic_2

subject:                    Math_2

Upvotes: 0

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