#! perl
use strict;
use warnings;
use Data::Dump;

while (<DATA>)
{
    chomp;                  # Trim trailing newline

    my @apts = /[- \d]+/g;  # Get all sequences of digits, spaces, & hyphens

    s/^[ ]+ //x for @apts;  # Trim initial  spaces
    s/ [ ]+$//x for @apts;  # Trim trailing spaces

    @apts = grep { /^\d{3,4}$/ } @apts;     # Get 3- or 4-digit sequences only

    dd \@apts;
}

__DATA__
John Smith lives in Apts. 123 & 456, home number: 555-6666-7777
Please phone Jane Doe on 111 2222 3333. She lives in apartment 789 in the Main building.
Please phone Janet Roe on 88899990123. She lives in apartment 100 in the Main building.