How to improve regex for parsing equals delimited data

[Lotus1]

I found out that one of my programs wasn't parsing the field values correctly due to unexpected white space inside the field values. What I came up with works but seems cumbersome. I used a positive lookahead for the first three fields.

Any suggestions for how to improve this or a better approach?

#!/usr/bin/perl
use warnings;
use strict;

while(<DATA>) {
    chomp;
    # original regex
    #if( /[A-Za-z]+\s*=\s*(\S*)\s*[A-Za-z]+\s*=\s*(\S*)\s*[A-Za-z]+\s*
+=\s*(\S*)\s*[A-Za-z]+\s*=\s*(\S*)/i ) {
    # Now trying to allow spaces in the fields without gobbling the fi
+eld names (which never have spaces)
    # This is getting cumbersome quickly.

    if( /^[A-Za-z]+\s*=\s*(.+?)(?=\s*[A-Za-z]+\s*=)\s*[A-Za-z]+\s*=\s*
+(.+?)(?=\s*[A-Za-z]+\s*=)\s*[A-Za-z]+\s*=\s*(.+?)(?=\s*[A-Za-z]+\s*=)
+\s*[A-Za-z]+\s*=\s*(.+?)\s*$/ ) {
    
        print "$1,$2,$3,$4\n";
    }
    else {
        print ",,,,not recognized: $_\n";
    }
}
    
 __DATA__
FIELDA = ONEAL FIELDB = RELAY FIELDC = L1208 FIELDD = ALTS
FIELDA = OSSIPEE FIELDB = DISC FIELDC = SOH: 169879251 FIELDD = DISC
FIELDA = OSSIPEE FIELDB = RELAY FIELDC = L1201 FIELDD = ALTS
FIELDA = OSSIPEE FIELDB = RELAY FIELDC = L1203 FIELDD = ALTS

Here is the desired output.

ONEAL,RELAY,L1208,ALTS
OSSIPEE,DISC,SOH: 169879251,DISC
OSSIPEE,RELAY,L1201,ALTS
OSSIPEE,RELAY,L1203,ALTS