# 813119.pl:
my @args=(0);
my $ filename = "ABC.pl";
@args = ("$filename com1@115200 65");
system(@args) == 0 or die "system @args failed: $?";
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# ABC.pl:
print join( ' / ', @ARGV), "\n";
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Mostly works for me. ABC.pl gets called, and displays

com1 / 65
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I'd recommend quoting the '@' character in your @args assignment, as in:

@args = ("$filename com1\@115200 65");
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Which changes the output to

com1@115200 / 65
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What output are you seeing? Which version of perl (perl -V)?