$ cat t.pl
use strict;
use warnings;

my @examples = (
    'Something something -something1 something eid- 1234 gkn 12-34_loanmaster',
    'Something :something something6 eid - 4532 gkn 34-21-hostmasfer',
    'eid 762 something something1 something@',
);

for my $v (@examples) {
    if ($v =~ /
                eid       # Prefix for the ID
                \s*       # might have some spaces
                (-\s*)?   # maybe a hyphen with more spaces
                (\d+)     # has one or more digits
            /x) {
        print "Found ID <$2> in <$v>\n";
    }
}

$ perl t.pl
Found ID <1234> in <Something something -something1 something eid- 1234 gkn 12-34_loanmaster>
Found ID <4532> in <Something :something something6 eid - 4532 gkn 34-21-hostmasfer>
Found ID <762> in <eid 762 something something1 something@>