Perl Regex unable to select word with Special character $ - regex

Question

I tried to split a string into words (one of the words has the special character $) , but the split didn't work. I want to split the string below into "Test" "Str$ing"
$test = "Test Str$ing";
my #words = split(" ",$test);
print "#words";
print "-------1End------------\n";
foreach my $str (split /(\s)+/, $test) {
print "$str\n";
}
print "-------End------------\n";
I executed the above code and got the below result, and, as you can see, the 2nd word is only half there:
Test Str
-------1End------------
Test
Str
-------End------------
Any help on this?

Answer 1

In Perl, a dollar sign inside a double-quoted string triggers interpolation. So this assignment:
$test = "Test Str$ing";
sets $test to the string Test Str followed by the value of the variable $ing. If $ing is not set (and you don't have strictures enabled, which would cause the program to fail at this point), the result is just Test Str.
To get a literal dollar sign you have to escape it with a backslash, or use single quotes instead:
$test = "Test Str\$ing";
# or
$test = 'Test Str$ing';
In any case, the first line in your program, after the #! anyway, should be use strict;. Then Perl will catch these errors and blow up instead of silently letting you shoot yourself in the foot. For good measure, you should add use warnings; too:
#!/usr/bin/env perl
use strict;
use warnings;
$test = "Test Str$ing";
Watch what happens when I try to run the above:
Global symbol "$test" requires explicit package name (did you forget to declare "my $test"?) at foo.pl line 5.
Global symbol "$ing" requires explicit package name (did you forget to declare "my $ing"?) at foo.pl line 5.
Execution of foo.pl aborted due to compilation errors.
Your program should look more like this, with minimal changes to pass strict:
#!/usr/bin/env perl
use strict;
use warnings;
my $test = 'Test Str$ing';
my #words = split ' ', $test;
print "#words";
print "-------1End------------\n";
foreach my $str (split /(\s)+/, $test) {
print "$str\n";
}
print "-------End------------\n";
That still seems odd to me, as you're printing all the words on a single line without a newline before the 1End sentinel, and then printing each of them on a line with blank lines between (not really blank, though - containing the whitespace from the original string). But if that's what you want, the above works. Output:
Test Str$ing-------1End------------
Test
Str$ing
-------End------------

Answer 2

You can do it with simple quotation marks:
#!/usr/bin/perl
$test = 'Test Str$ing';
my #words = split(' ',$test);
print "#words";
Otherwise Perl considers $ing to be a variable (which is empty).

Answer 3

The best practice to assign data to a variable is by using single quotes.
Ex:
my $var_name = 'TEST MESSAGE';
If the data which consists of variable and this is to be assigned to another variable then use double quotes. Data in double quotes will interpolated by PERL.
Ex:
my $var1 = 'TEST';
my $var2 = "$var1 MESSAGE";