This is your problem line:

@PSarray = $PScmd ;
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By that point, $PScmd already contains the result of the command. You are assigning all the lines to $PSarray[0].

There are two ways to fix your code, that I can see:

• Split the result into lines: @PSarray=split(/\n/,$PScmd);
• Or do the substitution on the whole string, but change how the RE engine interprets it: s/^\s+//m. (The m modifier tells the regexp engine to make ^ and $ match start and end of line instead of start and end of string).