I will answer your question below, but first, I strongly recommend not to use backticks to run shell commands for things you can do in Perl! For date/time handling, I prefer DateTime, but in this case you can probably just use the core module Time::Piece, plus the Perl builtin glob (Update: Make sure to read File::Glob, though, as it's got some caveats in regards to whitespace, which is why I use File::Glob ':bsd_glob' in the code):

use warnings;
use strict;
use Time::Piece;
use File::Glob ':bsd_glob';

my $today = localtime->strftime('%Y%m%d');
my $filename = glob('electric_inventory_WE_'.$today.'*.dat');
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I wrote about backticks and the potential security issues with them here.

The problem you are having with the code you showed can be solved by looking at item 3 on the Basic debugging checklist (unexpected whitespace), and using chomp on those variables.

there are better ways to grab dates and filenames (PS infact haukex was faster than me and shown you better ways), whithout shelling out..

Anyway i cannot confirm your issue: it works as expected; you must have some other errors

echo blur > 20170730_195758.dat

# warning windows double quotes!

perl -e "my $today = '20170730'; print `ls 20170730*.dat`"

20170730_195758.dat
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L*

i cannot confirm your issue

same mistake as OP

perl -e 'print ">>".`ls 20170730*.dat`."<<"'
>>20170730_195758.dat
<<
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