Inconsistency between perl grep and cli grep - linux

Question

I am doing the following:
#!/usr/bin/perl
use strict;
use warnings;
my $proc = `ps -ef|grep -c myscriptname`;
print $proc;
This prints 2 when I run it inside the script.
ps -ef|grep -c myscriptname on the command line just shows: 1
Why?
same for my $proc = qx/ps -ef|grep -c myscriptname/
UPDATE
To be clear I run this snippet from somerandomscript.pl
Update 2
Following the advice of edorqui I remove -c getting:
12013 15777 15776 0 14:11 pts/6 00:00:00 sh -c ps -ef | grep myscriptname
12013 15779 15777 0 14:11 pts/6 00:00:00 grep myscriptname Argument "12013 15777 15776 0 14:11 pts/6 00:00:00 sh -c ps..." isn't numeric in numeric gt (>) at somerandomscript.pl line 8
from inside the script

Answer 1

The ps -ef command is showing the grep itself.
To skip this behaviour, try grepping for a regex condition that does not match the grep itself:
ps -ef | grep myscript[n]ame
or whatever similar can make it:
ps -ef | grep myscriptnam[e]
Explanation
If you run a sleep command in the background:
$ sleep 100 &
[1] 9768
and then look for it with ps -ef:
$ ps -ef | grep sleep
me 9768 3673 0 14:00 pts/6 00:00:00 sleep 100
me 9771 3673 0 14:00 pts/6 00:00:00 grep --color=auto sleep
You get two lines: the process itself and the grep command looking for it. To avoid it and show just the process itselves, we can either:
$ ps -ef | grep -v grep | grep sleep
or use a regex in the code so that the grep process is not matched:
$ ps -ef | grep slee[p]
me 9768 3673 0 14:00 pts/6 00:00:00 sleep 100
because line
me 9771 3673 0 14:00 pts/6 00:00:00 grep --color=auto sleep
does not match in grep slee[p].
See explanation in a related topic.

Answer 2

I suposse your perl script is named "myscriptname".
When you run this script, you have a new process (perl myscriptname.pl), and it's showed by the ps -ef command. The other one is related to the grep command (it has the text you are looking for)

Answer 3

#fedorqui's answer is right on -- the grep is matching its own invocation in the process table, and perhaps that of its parent shell, too, though timing issues mean this does not always happen from the CLI.
However, another approach, avoiding grep in favor of perl, would be:
my $count = () = qx(ps -e -o cmd) =~ /myscriptname/mg;
# Now $count tells you the number of times myscriptname appears in the process table
See this answer for why the empty parens are used above. Note, too, that you don't need the full ps output (-f), you just want to match on the command name (-o cmd).

Answer 4

Take a look at the pgrep and the pkill commands. These are standard Linux commands are are way easier to use than trying to do a ps and then a grep.
Also, if you do use ps, take a look at the -o options. These let you display the columns you want, and give you a way to strip out the heading.