No they cannot be used interchangeably in all places, the word versions are specifically guaranteed to have lower precedence than the symbol versions (infact guaranteed to have the lowest precedence of any operators), you might care to try for instance:

open ONE, "somefilethatdoesnexist" or print "one: $!\n";
open TWO, "somefilethatdoesnexist" || print "two: $!\n";
[download]

As you can see the latter doesn't behave as expected as the '||' binds more tightly and ends up taking the value of the filename - infact the check is optimised away because this is essentially a no-op, as the output from B::Deparse shows:

print "one: $!\n" unless open ONE, 'somefilethatdoesnexist';
open TWO, 'somefilethatdoesnexist';
[download]

/J\

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.