If it will always be a constant number of fields per line, you could do something like this:

while(<>){
    chomp;
    my @line = split /\|/;
    while( @line < 4 ){
        $_ .= <>;
        chomp;
        @line = split /\|/;
    }
    if( @line > 4){
        warn "Found line with too many elements";
    }
    print join "|", @line;
    print "\n";
}
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