Use a capture () to extract the part you want

#!/usr/bin/local/perl
use strict;
use Data::Dump 'pp';

my @project_name = ();
while (my $line = <DATA>){
  if ( $line =~ m!\[(.*):/\]! ){
    push @project_name,$1;
  }
}
pp \@project_name;

__DATA__
cpfskTeam = sonkar, mobrien3, dokeeff2, pquinla, hkumar3

[cpfsk:/]
* = r
@cpfskTeam = rw
@serveradmins = rw
@svnadmin = rw
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