oh! well that's pretty simple, and you have a few alternatives.

{
    local @ARGV = ('file1', 'file2', ...);

    while (<>) {
        chomp;
        ...
    }
}
[download]

or

foreach $filename ('file1', 'file2', ...) {
    local *RPT;
    open(RPT, '<', $filename)
    or die("...\n");

    while (<RPT>)
    {
        chomp;
        ...
    }
}
[download]

or

sub read_log {
    my ($filename, $analysis_ref) = @_;

    local *RPT;
    open(RPT, '<', $filename)
    or die("...\n");

    while (<RPT>)
    {
        chomp;
        ...
            if (exists($$analysis_ref{$key}))
            {
                $$analysis_ref{$key} .= $msg;
            }
            else
            {
                $$analysis_ref{$key} = $msg;
            }
        ...
    }
}

my %analysis;
read_log($_, \%analysis)
   foreach ('file1', 'file2', ...);
[download]