Since the OP mentions that the "Y" will be at the end, why not use a [ -1 ] subscript to avoid the "defined" complication? You could also use a single push with the conditional and target arrays in a ternary. Some may find this less readable than the if ... else ... but I prefer it for simple "push to this or that depending" situations.

$ perl -Mstrict -Mwarnings -E '
open my $inFH, q{<}, \ <<EOD or die $!;
ws.abc.dsfsfsfwerfrwef std 13232
ws.dfsdferferfregregrgr std 99868 Y
ws.abc.asddwefewfewfewf std 45345
fwfrwfrefergegregerefds std 36754 Y
ws.abc.fferfergregrfreg std 45435 
EOD

my @streams;
my @spaces;

while ( <$inFH> )
{
    my @flds = split;
    push @{ $flds[ -1 ] eq q{Y} ? \ @streams : \ @spaces },
       $flds[ 0 ];
}

say qq{@streams};
say qq{@spaces};'
ws.dfsdferferfregregrgr fwfrwfrefergegregerefds
ws.abc.dsfsfsfwerfrwef ws.abc.asddwefewfewfewf ws.abc.fferfergregrfreg
$

[download]

I hope this is of interest.

Cheers,

JohnGG

In reply to Re^2: Perl : Split/Regex by johngg
in thread Perl : Split/Regex by sravs448

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