#!/usr/bin/perl
use 5.016;
use warnings;
use Data::Dumper;

my ($para, @para, $val, @val);
my $serverid = '';

local $/ = "[server";

while ($para = <DATA>) {
    chomp $para;
    if ( $para =~ /(\d+\])(.*)(?:\[server)*/s ) {
        chomp $1;
        $serverid = $1;
        push (@para, "server" . "$serverid: ");
        $val = $2;
        if ( $val =~ /^\n(.*)/s ) {
            $val = $1;
        }
        $val =~ s/\n/, /gs;
        push (@val, $val);
    }
}

my $i;
for $i( 0 .. $#para ) {
    $para[$i] =~ s/[\]]//;               # get rid of square brackets (if you must)
    say "$para[$i]$val[$i]";
}

=head OUTPUT:

C:\>1050631.pl
server1: /tmp/location1/file.log, /tmp/location2/file.log,
server2: /usr/loc1/file.log, /usr/loc2/file.log,
server3: /citrix/dir3/file.log, ,
server17: /etc/bin/dat/file.log, /etc/misc/logs/files3.log, ,


=cut

__DATA__
[server1]
/tmp/location1/file.log
/tmp/location2/file.log
[server2]
/usr/loc1/file.log
/usr/loc2/file.log
[server3]
/citrix/dir3/file.log

[server17]
/etc/bin/dat/file.log
/etc/misc/logs/files3.log

[server0Xff]
/won't be seen/file.log
/nor/this/file.log
/because/server_name/does not match regex in Ln13