PLayed with it a little changing the split from

my %h = map { ( split /=/, $_, 2 ) } split /,/;
to
my %h = map { ( split /=/, $_, 1 ) } split /,/;
and
my %h = map { ( split /=/, $_, 3 ) } split /,/;

print "$h{'msgagt'}\n" if exists $h{'msgagt'};
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Output was all the same.

ESM_WMB_AIX
Odd number of elements in hash assignment at parse_4_ovo.plx line 20, 
+<$out> line 3.
Odd number of elements in hash assignment at parse_4_ovo.plx line 20, 
+<$out> line 7.
Odd number of elements in hash assignment at parse_4_ovo.plx line 20, 
+<$out> line 9.
Odd number of elements in hash assignment at parse_4_ovo.plx line 20, 
+<$out> line 11.
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