Dollar symbol should be around entities and values- Perl - perl

Question

I have confusion with my code to remove dollars inside the digits (multi values) and to be inserted the dollar symbol around the values.
Sure I am little bit confused.
For e.g.: 10$x$10$x$10$x$10 should be $10x10x10x10$ #might be 'n' numbered infinite.
My code:
use strict;
use warnings;
my $tmp = do { local $/; $_ = <DATA>; };
my #allines = split /\n/, $tmp;
for(#allines)
{
my $lines = $_;
my ($pre,$matches,$posts) = "";
$lines=~s/(\d+)(\$*)\\times\$(\d+)/$1$2\\times$3\$/g;
print $lines;
}
Input:
__DATA__
where $Q=k-k^{\prime}$ is the scattering vector of length $4\pi \sin{\theta} /{\lambda}$ for a neutron of wavelength ${\lambda}$ scattered at an angle $2{\theta}$, and k and k' are X-ray absorption spectroscopy. Thus, RMC trials were performed for several samples assuming either A 10$\times$10$\times$10 supercell was first built, based on the unit cell model Sample paragraph testing 10$\times$10$\times$10 text continues.... Sample paragraph testing 10$\times$10$\times$10$\times$10 text continues.... Sample paragraph testing 10$\times$10$\times$10$\times$10$\times$10$\times$10 text continues.... obtained.
Required Output:
where $Q=k-k^{\prime}$ is the scattering vector of length $4\pi \sin{\theta} /{\lambda}$ for a neutron of wavelength ${\lambda}$ scattered at an angle $2{\theta}$, and k and k' are X-ray absorption spectroscopy. Thus, RMC trials were performed for several samples assuming either A $10\times10\times10$ supercell was first built, based on the unit cell model Sample paragraph testing $10\times10\times10$ text continues.... Sample paragraph testing $10\times10\times10\times10$ text continues.... Sample paragraph testing $10\times10\times10\times10\times10\times10$ text continues.... obtained.```

Answer 1

If you simply want to blindly transform 10$x$10$x$10$x$10 into $10x10x10x10$ without taking account anything about the surrounding text, then this should be enough.
$lines=~s/(\d+)\$/\$$1/g;
If your requirements are more complex than that, you need to update the question with the details.
[UPDATE]
Just looking again at the input and expected output, I see there is a complication -- some of the input looks like this times$10$ with the expected output times$10. That means we have an optional leading $ that needs to be taken into account.
To deal with that we can add \$? to the start of the regex to match the optional $, like this
$lines=~s/\$?(\d+)\$/\$$1/g;
Below is a rewrite of your code that also removes some of the unnecessary splitting
use strict;
use warnings;
while (<DATA>)
{
s/\$?(\d+)\$/\$$1/g;
print ;
}
__DATA__
Sample paragraph testing 10$\times$10$\times$10 text continues....
Sample paragraph testing 10$\times$10$\times$10$\times$10 text continues....
Sample paragraph testing 10$\times$10$\times$10$\times$10$\times$10$\times$10 text continues....
Output is
Sample paragraph testing $10\times$10\times$10 text continues....
Sample paragraph testing $10\times$10\times$10\times$10 text continues....
Sample paragraph testing $10\times$10\times$10\times$10\times$10\times$10 text continues....
[UPDATE 2]
Assuming the actual requirements are
change the first occurrence of, say, 123$ into $123
for last occurrence of $123, change to 123$
for the intermediate digit-dollar sequences, remove the dollars.
use strict;
use warnings;
while (<DATA>)
{
# replace the first occurrence only
s/\$?(\d+)\$/\$$1/;
# remove $ from the all but the last digit-dollar
# uses lookahead to prevent matching the last digit-dollar
s/times\$?(\d+)\$?(?=\\t)/times$1/g;
# rework the last occurrence of digit-dollar
s/times\$(\d+)/times$1\$/;
print ;
}
Input:
__DATA__
Sample paragraph testing 10$\times$10$\times$10 text continues....
Sample paragraph testing 10$\times$10$\times$10$\times$10 text continues....
Sample paragraph testing 10$\times$10$\times$10$\times$10$\times$10$\times$10 text continues....
output is
Sample paragraph testing $10\times10\times10$ text continues....
Sample paragraph testing $10\times10\times10\times10$ text continues....
Sample paragraph testing $10\times10\times10\times10\times10\times10$ text continues....
UPDATE 3
New requirement -- there can be multiple digit-dollar sequences in a single line.
This complicates the code a bit, but not much.
use strict;
use warnings;
while (<DATA>)
{
# walk the string looking for strings of the form "10$\times$10$\times$10$\times$10"
while (s/(.*?)((\$?\d+\$?\\times)+\$?\d+\$?)//)
{
# output any data that preceded the digit-dollar sequence
print $1;
my $block = $2;
# Remove all dollars
$block =~ s/\$+//g;
# put back the initial dollar
$block =~ s/^(\d+)/\$$1/;
# and the terminating dollar
$block =~ s/$/\$/;
# output the modified digit-dollar sequence
print $block;
}
# output trailing text
print;
}
Input:
__DATA__
where $Q=k-k^{\prime}$ is the scattering vector of length $4\pi \sin{\theta} /{\lambda}$ for a neutron of wavelength ${\lambda}$ scattered at an angle $2{\theta}$, and k and k' are X-ray absorption spectroscopy. Thus, RMC trials were performed for several samples assuming either A 10$\times$10$\times$10 supercell was first built, based on the unit cell model Sample paragraph testing 10$\times$10$\times$10 text continues.... Sample paragraph testing 10$\times$10$\times$10$\times$10 text continues.... Sample paragraph testing 10$\times$10$\times$10$\times$10$\times$10$\times$10 text continues.... obtained.
Sample paragraph testing 10$\times$10$\times$10 text continues....
Sample paragraph testing 10$\times$10$\times$10$\times$10 text continues....
Sample paragraph testing 10$\times$10$\times$10$\times$10$\times$10$\times$10 text continues....
output is
where $Q=k-k^{\prime}$ is the scattering vector of length $4\pi \sin{\theta} /{\lambda}$ for a neutron of wavelength ${\lambda}$ scattered at an angle $2{\theta}$, and k and k' are X-ray absorption spectroscopy. Thus, RMC trials were performed for several samples assuming either A $10\times10\times10$ supercell was first built, based on the unit cell model Sample paragraph testing $10\times10\times10$ text continues.... Sample paragraph testing $10\times10\times10\times10$ text continues.... Sample paragraph testing $10\times10\times10\times10\times10\times10$ text continues.... obtained.
Sample paragraph testing $10\times10\times10$ text continues....
Sample paragraph testing $10\times10\times10\times10$ text continues....
Sample paragraph testing $10\times10\times10\times10\times10\times10$ text continues....